Aquatic Snakes of Southeast Asia

Features: Homalopsine snakes are found in freshwater and marine habitats from India to northern Australia and exhibit a wide diversity of form and function. These water snakes are characterized by dorsally-oriented eyes and valvular nostrils. Some species are marine (the keel-bellied water snake, Bitia hydroides), some occur mainly in mangrove swamps, estuaries and coastal rivers (the crab-eating water snake, Fordonia leucobalia, and the dog-faced water snake, Cerberus rynchops), and others are found in freshwater streams and lakes and are semi-aquatic (the rainbow water snake, Enhydris enhydris, and the plumbeous water snake, Enhydris plumbea).

The homalopsines are rear-fanged snakes. Toxic secretions from glands in the back of the mouth drip into grooves on the rear teeth when the snake bites its prey. Most homalopsines are small and are not considered dangerous to humans. The diet of most homalopsines consists of fish and frogs, although at least one species specializes on crabs (crab-eating water snake, Fordonia leucobalia). All homalopsine snakes bear live young.

The homalopsines are particularly interesting because they offer a fascinating evolutionary case study in the morphological, physiological, behavioral and ecological changes associated with the shift from terrestrial to marine life styles.

Field projects have been conducted in Malaysia, Singapore, Cambodia, and Thailand.

Field Projects:

The Homalopsinae (Oriental-Australian rear-fanged water snakes) is a small (34 species, 10 genera) colubrid subfamily notable for its ecological and morphological diversity. A molecular phylogenetic study of the homalopsines based on partial sequence of three mitchondrial genes (12S and 16S ribosomal RNA and cytochrome b) from 14 ingroup species, five Old and New World natricines and the Old World colubrid, Dinodon semicarinatus was conducted by Voris et al., 2002.

Homalopsine monophyly was strongly supported with respect to the outgroups included in our study. Cantoria violacea, a morphologically distinctive marine crustacean eater, formed the sister group to the rest of the homalopsines. Enhydris, the most species-rich genus in the subfamily, was polyphyletic with respect to other homalopsines although five morphologically and ecologically similar species formed a well-supported clade. The marine crustacean eaters Fordonia leucobalia and Gerarda prevostiana, also formed a novel clade.

The evolutionary and ecological implications of this phylogeny for the Homalopsinae are discussed in more detail in the following publication: Voris, H.K., M.E. Alfaro, D.R. Karns, G.L. Starnes, E. Thompson and J.C. Murphy. 2002. Phylogenetic relationships of the Oriental-Australian rear-fanged water snakes (Colubridae: Homalopsinae) based on mitochondrial DNA sequences. Copeia 2002(4):906-915.

A printable PDF version of this publication is available. Please contact Kathleen Kelly.

Literature:

Gyi, K.K. 1970. A revision of the colubrid snakes of the subfamily Homalopsinae. University of Kansas Publications 20(2):47-233.

Our projects on the water snakes of Southeast Asia are based at The Field Museum of Natural History but they have involved many collaborations and a great deal of assistance and cooperation from many colleagues and students from many countries.

Project leaders include Daryl R. Karns, Professor of Biology at Hanover College, Hanover, Indiana and Research Associate at The Field Museum; John C. Murphy, Chairman of the Science Department, Plainfield High School and Research Associate at The Field Museum; and Harold K. Voris, Curator and Head of the Division of Amphibians and Reptiles at The Field Museum.

Sea Kraits

Features: Amphibious sea kraits are characterized by one feature that is an obvious aid in swimming, a broad paddle-like tail. It shares other features such as broad belly scales and lateral nostrils with its terrestrial relatives. The life history and ecology of the brown-lipped sea krait (Laticauda laticaudata) and the yellow-lipped sea krait (Laticauda colubrina) have been studied in New Caledonia (Saint Girons, 1964), Fiji (Guinea, 1994; Shetty, 2000) and Borneo (Voris & Voris, 1995).

History:

The amphibious sea kraits (previously Laticaudidae) are a small group of amphibious snakes that occur from the Bay of Bengal to the South Pacific Ocean. They belong within the elapid snakes (coral snakes, cobras, kraits, etc.). Elapids are characterized by a hollow fixed front fang and neurotoxic venoms. The relationships among sea kraits has been studied by Voris (1977) and McCarthy (1985) and the relationships of sea kraits to other elapid snakes have been studied most recently by Keogh (1998).